I glued up my tube from one piece of PVC, no sewing at all just a 1cm overlap and glued. 10oz fabric is pretty light and flexible about like a raincoat. 1mm sounds really thick and stiff.

I think you might be over estimating the ability of elephant trunks to actually do their job. Nothing except a boat with no transom at all will empty "within seconds."

If you stuff the bow once the most important thing you can do is reduce speed and/or change course immediately. Any boat 1/3rd full of water is riding low so you're highly likely to stuff the bow again. The second wave will carry in ALOT more water and swamp the boat to the gunnels. No matter what its going to take a few minutes to get back to normal, depending on speed, bow rise and if any more water is coming aboard.

Plus my transducer needs to find a new home somewhere on the starboard side where the transom wheels and future home of the elephant trunk aren't going to be located.

Stainless is a pain to drill, but easy enough to weld. Aluminum is easy to drill, but for me a pain to weld.

I'm interested to see what you come up with. There's not much room on the transom for all that. I've been having a hard time finding a suitable location to mount my transducer. Sounds like our boats are similar, so please keep us posted.
Remember when drilling stainless, low speed, high feed, and lots of oil. No problem.
Good luck, and Merry Christmas!

I'm interested to see what you come up with. There's not much room on the transom for all that. I've been having a hard time finding a suitable location to mount my transducer. Sounds like our boats are similar, so please keep us posted.
Remember when drilling stainless, low speed, high feed, and lots of oil. No problem.
Good luck, and Merry Christmas!

Don't forget the trailer bunks getting in the way too! You do not ever want to have anything you have to remember to pull or move before putting the boat on the trailer. It can be an expensive mistake when you or someone else trashes a transducer. I have seen it before. All my boats have been setup to pull right up on their trailers, even with fenders in place.

I found this at HF and other places. Might just be the ticket assuming it goes over a 3" stainless pipe I still need to locate first.

Hi peter-c
the boat in the photos is mine and dont worry about using the photo,s thats what they were put on this site for in the first place ,glad they could be of use ,

i used to have a Humber 16 ft heavy duty work boat SiB and that only had a single 3inch diamiter drain trunk and it coped well with any water that came aboard ,, it was only glued into the hole on the wood transom and did not have any other fittings unlike the y boat in the pics which has fittings like cptn jacks ,,and was made from a tube of hypalon materiel,,
in all the years i had it it never started to come loose.

as a matter of intrest the y boat trunk holes are 3" 1/2 inches in diameter,,
reason that its a bit over kill on an 11 ft boat is that its a standard fitting on the next size up boat the RNLI use the ,,D class at 16 ft ,,as there are more d class boats than y boats it makes sense to use the availble fittings when building them,

you may have seen it before but this clip shows example of one of the d class boats being launched and how fast the trunks work .

The drain is only going to work while moving forward (unless your boat is on the trailer.) having it seal up (mostly) by collapsing isn't that big a deal; you simply drop them just prior to hitting the throttle, and pull them up before stopping (if you're worried about swell or wakes), or just after you've drained the water (in a non-recurring type of event.)

Not sure you really need to go three inches, but if you have the room on the transom, bigger is probably better. My boat (which you've seen) is running two 1.5" trunks to drain the deck (bilge is by electric pump.) I doubt you're going to get a solid 3" stream of water exiting the boat anytime you're in the water: if totally swamped, you'll have problems getting the trunk high enough to clear the waterline; if you have a small enough amount of water in the boat to plane up, you won't have enough water to span the trunk diameter.

If you want to go some other size (meaning I think your PVC drain tube material is fine), simply glue up a piece of PVC or hypalon in the appropriate diameter and stick it on. Hose clamp around, glue to the tube, or any other waterproof method will work fine. The tube mount will be clear of the water while underway. Flow through the tube will not be an issue, so seam restriction won't matter. No substantial strength needed, so I wouldn't worry about stitching it (the most stress it gets is from directing non-pressurized water out the back; sort of like the stress a garden hose is under while funneling water from a pitcher through it.)

As far as your 3" stainless tube, OnlineMetals.com has 304 welded tube in 3" OD for about $25/ft, or seamless for a few bucks more (thinwall; thickwall gets expensive pretty quickly.) They have other sizes if desired.

Weld a flange (or partial flange, if flush-to bottom) to the tube, cut tube to about 2 to 3" longer than the transom thickness, drill and seal the transom, slide through from inside, bolt or screw it in (seal all holes thoroughly), attach whatever trunk material, rig up a line to retract, secure, and deploy, and you're good to go.

cptnjack, nice boat! What did you wind up making the actual elephant trunk from? Do you know the thickness? From my internet arm chair it looks like very stiff material. I wonder if slicing the ends would help it flatten out to seal from water intrusion? Sewing the last couple inches of material definitely would flatten it out.

I bought enough stainless 316 3" tubing to make two elephant trunks although I am only going to use one. Happened to be a pre-cut piece the dealer had around. Even still expensive stuff at $25 cash. I then went to a farm supply and bought a few feet of 3" discharge hose as I posted above. I am not happy with it though as it seems too stiff. Looks kinda like what you have, but it is blue. The pvc tubing fits the stainless tubing pretty well and could easily be clamped up with some sealer between. Not sure which material I am going to use for the trunk yet.